Electrostatic spinning of polytetrafluoroethylene (PTFE) into continuous fiber allows for the formation of non-woven sheets, tubes, and coatings with potential for multiple other applications and forms. The process of electrostatic spinning is well known in the literature and the patenture as represented by U.S. Pat. Nos. 2,158,416; 4,432,916; 4,287,139; 4,143,196; 4,043,331; 4,689,186 and 6,641,773 each of which is incorporated herein by reference thereto. While most of these patents pertain to soluble polymers or thermoplastics, none pertain directly to the formation of fibers or mat from virtually insoluble polymers or those that do not flow readily on heating to elevated temperatures. A review of the literature and patenture revealed limited reference to the process whereby a polymer that meets the properties of limited solubility and inability to readily flow upon heating such as PTFE can be formed into a fiber suitable for electrostatic spinning into various structures. U.S. Pat. Nos. 4,323,525 and 4,044,404, both of which are incorporated herein by reference, provide information related to processing and electrostatic spinning of PTFE from an aqueous or other dispersion.
However, such conventional processes have several shortcomings. Such processes describe the use of low viscosity PTFE dispersions (15,000 cPs) which do not result in uniform or consistent fiber formation. Furthermore, such processes describe the use of a grounded spinning head and a charged target. Observation shows various levels of degradation in samples produced by reverse polarity. Conventional processes also fail to accommodate for shrinkage of a mat during sintering.
Thus, a need exists for processes that address the deficiencies described above. Materials made from such processes would also be particularly beneficial.